docs: def filter_intensity(df, label="", with_multiplicity=False):
      """
      Filter to include only the Intensity values with optional specified label, excluding other 
      Intensity measurements, but retaining all other columns.
      """
      label += ".*__\d" if with_multiplicity else ""
  
      dft = df.filter(regex="^(?!Intensity).*$")
      dfi = df.filter(regex='^(.*Intensity.*%s.*__\d)$' % label)
  
      return pd.concat([dft,dfi], axis=1)